Since Fire Emblem has been around for more than 20 years, the script writers have managed to slip sexual innuendos in the dialogue more than once. The absolute winner is Fire Emblem Awakening, the newest (as of 2014) entry in the franchise, which has more innuendo than all the other games combined:
Fire Emblem: Blazing Sword (or just Fire Emblem in the States) has some dark moments for an E-rated game. Specifically, the ending you get when Bartre and Karla are paired; Karla dies of illness after giving birth to Fil/Fir. Bartre "takes their daughter to her uncle and joins Karla."
This might actually be a Dub Induced Plothole ...but given that there were no plans to release Fire Emblem 6 out here, they figured they'd probably rather just imply that than state what really happened - Bartre is alive and well in Fire Emblem 6.
Though there is a more genuine example in Eliwood and Ninian's C support:
Eliwood: Hrm... Ah, I know! Next time you are free, show me your dancing! Not one of the little dances — something special.
In the Summer Scramble DLC chapter, Nowi contemplates Tharja's boingy bits and feels her up. Yes, this is in the American version (though it didn't get past the European radar, as they changed it to Nowi discussing Tharja's "beautiful and silky" black hair)
Nowi (paraphrased): "You're the biggest one. Trust me!"
Also, when Nowi's daughter Nah shows up, she will be all "What did my dadsee in my mom?". In the original Japanese, she'll accuse her father of being into little girls (sorta, since this isNowi we're talking about); in the English release, she'll be convinced he knocked her up and married her FAST because of that. (And yup, Henry can be one of Nah's potential daddies, meaning that he does keep his "promise" if he marries Nowi. Again: Wow, Henry, WOW.) And the Lolicon elements are still present even in the English release, since Nah's father ends up telling her at the end of their A-support conversation that he was indeed attracted to Nowi because of her youthful appearance.
Actually, for all of his childish behavior, Henry himself seems to be pretty good at this trope. In his B support with Cordelia...
Henry: Hey, Cordelia! Thanks again for the sweet scarf!
Cordelia: Not at all. I'm glad you like it. *siiiiiigh*
Olivia: Hee hee! I guess you DO know Basilio pretty well after all!
In Severa and Brady's C Support, Severa says that they should start a "S&B Society."
It's not the only allusion to S&M. In the Laurent/Noire S support, Laurent is thrilled at the prospect of his girlfriend-to-be's Split Personality outbursts — revealing himself as a potential masochist who gets off at being verbally abused. (At least by Noire's "other self").
Then there is Vaike and Tharja's C support. When Tharja says she finds the Avatar fascinating, Vaike's reply is... special.
And let's not forget that, according to the Harvest Scramble DLC, Sumia apparently has a fetish forcrossdressing girls. Including a rather epic rant about it and trying to rope Sully into dressing up as a guy.
In the Future Past DLC, Grima in The Avatar's body taunts Lucina via mentioning how much her father Chrom was loved by the Avatar, aka the person who owned the body he's inhabiting. The catch is that the dialogue does not really change either when a female Avatar is married to someone else than Chrom... or even more so, when the Avatar is a male — and maybe even Lucina's boyfriend/husband. That Chrom dude is damn popular with girlsand guys, isn't he?
Also, in his C support with Frederick, Virion goes on about how he enjoyed a "brief but fruitful collaboration" with some noble ladies to give them some "respite from their dreary lives" through "romance's sweet perfume". That's not slipping under the radar, that's dancing in plain sight wearing neon lights and still getting by.
What the Merchant!Anna says to Gaius in Summer Scramble when he puts on a swimsuit:
Olivia isn't the only one riding on the high of pies. Perhaps it's just this troper reading too much into it, but Chrom and Sumia's S-support and the slang term for "pie" often used in modern language leads to what pretty much results in Sumia asking Chrom if he wants to eat her pie every day. ...yeah.
Pretty much all of her event tile and level up quotes are this. She's, in example, the only potential mother who asks her child (girl!Morgan) for perfume as a gift, and not to mention her Love Confession to the male Avatar has her cheerfully giving him Marshmallow Hell... hm.
If Gerome is Morgan's father, and the two step on an event tile, it can lead to the following quote. It likely refers to Gerome's desire not to leave an impact on the past, but it could be taken in a dirtier way, especially since he specifically mentions "fathering" Morgan.
Gerome: "I certainly can't believe I fathered you. I go through great pains not to leave a mark."
During Chrom's S support with the Female Avatar, he drops this gem: